Will,

If you're reading this, it means that one of several important things has just happened in your life: you had your parabatai ceremony, you're getting married, or I died. Honestly, I'm hoping it's the first one. The Angel knows you need an Alec. He saved my life more times than I can count. If it wasn't for him, you might not be here! Thank him next time you see him. Next, let me establish something: your name is William James Herondale. You go by Will. You are a Herondale. You're a Herondale. You're last name is Herondale. Your mother, Clary Fairchild, married me, Jace Herondale, and you are our first born son. YOU. ARE. A. HERONDALE. Remember that always. Don't let anyone try to convince you otherwise. If they try to, they're lying. You are a Herondale, and there aren't many of us, so remember that whenever you plan on doing something incredibly stupid in your life.

Speaking of you, it all started with two words: "I do". Your mother and I got married in July, and you were born in April. You're a smart kid (or we wouldn't have kept you this long!), so do the math. Figure it out. … … Yeah.

You made your mother one moody woman! Trust me, son, she was more demon than angel those nine months—and it's all your fault. I only hope that karma is just. But I remember the day you were born, and it was the happiest day of my life. (Never repeat that.) We named you William after an ancestor of mine. And you were the beginning of a new Herondale legacy, so you needed a good Herondale name. You know Jem and Tessa Gray-Carstairs, right? Well, they knew your namesake, the original Will Herondale. And from what I know from them of him, you've lived up to the name. And then there's 'James'. It's a nice name, certainly, but do you really think your mother and I would do anything without having a purpose? We're not that vain! Jem's real name is James, and he was Will's parabatai. He's never told you that, has he? He's also never told you that he was engaged to Tessa (whom both he and Will were in love with) over a hundred years ago and that he was addicted to the demon poison yin fen because he was tortured with it by the demon that killed his parents and that he ran out of it at one point and almost died, so he became a Silent Brother when he was seventeen, because it was the only way to save his life. And then Will married Tessa, and they had kids who got married and had kids, and they got married and had kids, who got married and had your great-grandfather, who got married and had your grandfather, who got married and divorced and remarried and had me. So thank Jem, too, because without him you wouldn't be here. And this is another reason I hope I gave you this to celebrate your parabatai ceremony, because they will literally do anything for you, even give up their fiancée. (Yeah. So I hope you thought about that before you chose!) Don't let me down, kid. You're named after two great people; you've got good blood, and your parents are devastatingly beautiful. Don't screw it up. So far, you haven't.

There were times when I tried to convince your mother to throw you out. I figured a good mundane family would adopt you, or else I was just going to send you to live with Simon and Isabelle and your cousins. Your mother didn't go for it. You should thank her. I imagine you acted like I would have had I not spent my childhood with an evil overlord trying to turn me into a mindless killing machine and who had another son at another house by the same name and who faked his own death. You know the stories. Your Grandpa Valentine was something out of a horror novel. But, damn, was I upset when he was killed, even though he deserved it. In a way, he was still my father. He had raised me, and I had loved him. So, by telling you all this, I'm saying that if I am dead when you read this, I hope you miss me. Or are at least upset. Even if I'm a crappy father, I hope you love me.

So, yes, karma got her revenge on me with you. You are very much like me, and you always have been, unfortunately. From the day you turned five, you kept asking me when you could get your first Mark. That was a long five years for me. Very. Long. But I was proud (and relieved) when that day finally came. Your mother was scared, but you're a Herondale. I knew that you'd be fine. Plus, we already had your brother and sister by that point, so even if something went wrong and you turned Forsaken and died, we had a few backups. But all went well, and from that moment on, you were a training fiend. That made me proud. Granted, you had been wielding seraph blades for years already (secretly, of course. Your mother must never know this!). But you were a natural with every other weapon. Again, this is thanks to your wonderful genes. Thank your loving parents. Unfortunately, you also inherited the Herondale piano hands, but you showed no aptitude for it. It's rather tragic how bad you are actually. Don't worry too much, though. Those long fingers are good for other things. (If you're fifteen or older reading this, you know exactly what I mean.) And you don't paint like your Grandmother Jocelyn or draw like your mom. We were afraid that we had done something to you before you were born that made artistically inept. But when you were about six, Jem (bless that man—THANK HIM, WILLIAM!) suggested that you try violin, and praise the Angel, we finally found something you were good at! You took to it quickly after the initial few months of sounding like Church being set on fire, and Jem was always patient with you. Your mother was so proud. I was just glad that you weren't mentally handicapped.

Thankfully, you were only about twenty months old when Zach was born. You didn't whine the way you did when Charlotte was born and you were nearly four. As your father, I'm obligated to say that I love all three of you equally. I'm fairly certain that's how parenting works. Again, please take into consideration that any parenting blunders I or your mother or your aunts and uncles have made are because we had few decent parental figures when we were your age. Simon's dad died when he was a kid, and his mom worked constantly. Not to mention when she freaked out and banished him from the house when she found out he was a vampire. Valentine experimented on your mother and I before we were born, stole the Mortal Cup, and tried to stop the Accords and create a new race of Shadowhunters by kidnapping angels and summoning Greater Demons. He also killed me. Robert and Maryse Lightwood weren't terrible, except that Robert hated Alec for awhile because he was gay, and Maryse told her seven-year-old daughter about the affair her husband had before their youngest son was born and proceeded to be rather distant throughout her children's lives. Oh, and she tried to throw me out once. And now you see. I hope I've never made any of these mistakes with you or your siblings, and I hope I never do. So, I'm telling you all this now. I love you. I love Zach. I love Charlotte. And I love your mother. I love Alec and Izzy, and, yes, even Simon and Magnus, and I would never do anything to tear this family apart. Trust me on that. If you knew what I went through to get them, you would understand how sincere I'm being. I would do anything to ensure that you would all always be safe. But with Shadowhunting in your blood, there is no such thing as safe. Learn that. It doesn't make it easier, but it's the truth. And knowing is better than not knowing. Every time.

Now, in case I have in fact perished in some epic battle with a demon, and your mother handed you this letter after my body was burned (as I have instructed her to do), I should probably tell you the paternal wishes I have for you. And, even if I'm alive and kicking (as I plan to be), it's a good father-son bonding thing. At least I've heard it is. Alec and Clary both said it was a good idea, and I trust them more than anyone else in the world. Anyway, when you grow up…I want you to be a Shadowhunter. If you decide to leave, please wait until I'm dead to do so. I would like you to find a parabatai before you turn eighteen. I was lucky enough to have found one, and it was one of the best decisions of my life. It's right up there with following your mother and Simon into that coffee shop. But don't pick just anyone. It has to be someone you connect with, someone you would die for. And it's not a decision to be taken lightly. Of course, you may already know this. You may already have your parabatai, and if you do, I still expect you to read this section, because I'm your father and I took the time to write it.

I would like you to get married, too. Preferably to a Shadowhunter. In reality, you'll probably marry a Shadowhunter girl whose life you saved. She probably won't know that she's a Shadowhunter, though. That's the type of girl Herondales tend to fall for. It runs in the family. Your mother told me not to say that. She said it sounds bad, that I should be supportive of you no matter whom you choose to love, but really a normal Shadowhunter-Shadowhunter marriage would be nice, considering your family tree. Jocelyn married a werewolf. Alec's married to a warlock. Isabelle married Simon, who was a mundane and then a vampire and then a mundane again and then a Shadowhunter. And I married your mom, who I thought was a mundane…and then thought was my sister…You should know that I really don't care whom you marry, though, as long as you love her. Or even him. If you decide that girls are too much of a hassle (they're not), then that's okay. You may end up with a diva warlock who looks like a gay Sonic the Hedgehog, and that's okay…well, kind of. I was referring to Alec, but if you end up with a diva warlock who looks like a gay Sonic the Hedgehog, then there are either two Magnuses or you took him away from Alec. And if you take him away from Alec, I will disown you. And kill him (if I'm not dead right now). Whomever you marry, don't rush into it. Love them. Love them more than you love yourself. Make sure they make you a better person, and make sure they feel the same about you. You should be equals. Yes, you should be equals with a woman. In reality, though, she will be much better than you, but you'll know she's the right one when she says that you're equal. But she will be aware that she's better than you. Because that is always true. Accept that now. Even the bravest, most handsome, most charming man alive (me, if I'm alive now or Channing Tatum if I'm dead (your mom used to like him)) is not as good as his wife. Respect her. Appreciate her. Love her. And if I ever hear of you mistreating a woman, I will disown you. And I'm serious. I have two other children to pile my hopes and dreams onto; I can afford to disown one.

I would like it if you were to have children in the future. Like I've said, there are only four Herondales left in this world: me, you, Zach, and Charlotte. We could use a few more. We were a pretty badass family at one point; let's get back there. That being said, if I die before you have children (or am dead now), 'Jace' is a wonderful name. (And I will know if you don't use it.) Other acceptable names include Alexander, Luke or Lucien, Max or Maxwell, Jonathan, Clarissa, Isabelle, or Amatis. No descendent of mine shall be named Sebastian, however. (Again, I will know.)

But before you get married or have children, I'm telling you this: don't rush into it. I don't care how in love you are with her. The only reason you should rush into a marriage is if she's pregnant. And if she's pregnant, I will disown you. But I will continue to support the baby. Shadowhunters marry young; they marry once; and they marry for life. You get one shot. Don't screw it up. And that goes for after you're married, too. If you cheat on her, I will disown you. You are a Herondale, and Herondales are nothing if they're not honorable. You remember the Will/Jem/Tessa story I mentioned earlier? When everyone thought that Jem was dying, Will told Magnus (yes, Magnus knew the original Will Herondale, too) that he would never be with Tessa after Jem died because it would be an insult to Jem's memory. It would seem like he had been waiting for his best friend and parabatai to die so that he could be with his fiancée. And Jem will tell you that Will loved Tessa like he loved being a Shadowhunter. It was something innate in him, something completely carnal. It was in his blood to love her, but he was willing to give that up because of his love and promise to Jem. That is honor, Will. That is love. Follow that code, and you won't go wrong.

In the same line of thinking, your mother and I probably got married too young. I proposed on her eighteenth birthday, and Jocelyn had a fit. She still didn't like me too much then, but she was coming around. Always ask the girl's parents for permission to marry her. I didn't, and I thought that Clary and Jocelyn were going to kill me. That was a mistake. Now, I'm not saying that I regret marrying her. Never think that. I love your mother more every day than the day before. And I will continue to love her more until the day I die (which may, at this point, have already happened…), and even then I won't love her as much as she deserves to be loved. (If I am dead when you read this, make sure you let her read that part.) We would have gotten married that fall, but, again, Jocelyn went hysterical. She married Valentine when she was nineteen, and you know how that turned out, so you can see why she was a little anti-teen marriage. So, to get around that, we were smartasses and got married as soon as we were both twenty. And then a few weeks later, we discovered we were pregnant with you. It was a pretty crazy time in our lives. You're mom couldn't even (legally) drink when you were born. We were very much still children. We were very much still children when Zach and Charlotte were born. Hell, I'm still a child now, albeit a very good looking, Marked, and heroic one. The point is, we lived by the mantra "Shadowhunters die young", your mother and I. Don't— even — think— about— it. You'll live plenty long enough to get married and have kids if that's what you choose. I love you, Will. I love you so much, and I would never change having you, but raising you was one of the hardest things I've ever done. You are the only thing I've ever been afraid of. Sure, I've been scared of losing people I love, your mom, Alec, and Isabelle especially. I've been scared that I was a monster. I've been scared that I had to be perfect or I wouldn't be loved. But you. Even though my childhood was awful, I always knew that it wasn't my fault. I knew who to blame: the man who raised me, my father. And I didn't want to ruin your life. What if you didn't have someone like Alec or your mom to pull you out of the darkness like they did for me? I was afraid, for the first time in my life, that I wasn't good enough to do something. I didn't think I was good enough to raise you. Thankfully, your mother told me to get over it and change your diaper. (THANK HER.)

Congratulations, William James Herondale. You either have a new parabatai, a new spouse, or you're free of me. (I really hope it's the first, still. I'm, like, thirty. I can't die yet!) So, I've now given all the fatherly advice that I'll ever possess, and I'm about to edit this letter and replace your name with Zach's. I'm glad you two get along so well, for the most part. Keep that up. He'll get you out of major trouble one day. Having a sibling is like having a (or another) parabatai. You are lucky, Will. (THANK YOUR PARENTS FOR THE FORETHOUGHT TO GIVE YOU SIBLINGS.) Take care of Charlotte, too, not that I think she'll need it. She's your mother's daughter and Isabelle's pseudo-niece, that's for sure. In my letter to her, I'll have to detail how she needs to take care of you. But she is your sister. When some lowlife scum inevitably breaks her heart, don't let her murder him. I don't want the Herondale name tainted with murder. Though I'm sure she'd be more than capable of succeeding at it. Be nice to her, and don't give her too much crap. She will hit you for it, and your mother and I will let her. She's a good kid. She and Zach both are. And you're their older brother, so they look up to you in one way or another. Don't abuse that power. It's a blessing and a curse.

You are the most wonderful son I could ever want, and you are definitely more wonderful than I deserve. I don't tell you enough, but I love you.

Ave atque vale (but hopefully not. Hopefully, it's just "See you at dinner"),

Dad