Author's Note
Just an author's note to answer the reviews, so that you don't have to wait until Season 6, which I am currently in the process of writing. So far, I am on 6x08. (For future reference, I would suggest making an FF account, or if you already have one, logging in before reviewing. It would make it easier to respond to everyone's reviews if I've already finished a season, as I could just PM you.)
Cole is a draconic guardian, which are akin to Whitelighters. However, unlike Whitelighters, who have multiple charges, draconic guardians are assigned to specific people. Cole was assigned to the Charmed Ones and their progeny, which is why he is never seen "working" like Leo. He would primarily be at the manor, in case his charges needed something, or out socializing, which I can't see Cole doing, unless it was with, like, Darryl. He's never seemed very social to me.
As for the differences between Prue and Piper regarding how they are during their pregnancies and being mothers, that was actually intentional on my part. Prue has always been very confident, while Piper has always been more of a worrier. So I figured that Prue would be more relaxed as a mother, while Piper would be a nervous wreck, like in canon.
As for the twins and Pagan, and their role in Chris's Dark Future, read S6 and find out. :)
Regarding Phoenix's actor and Persephone's actress, I assumed that people would do this on their own, but apparently not. Prue and Cole actually both have green eyes, according to the wiki, so just picture the actor and actress I picked for the twins with that eye color. It's difficult enough to find actors/actresses, especially baby/child actors, so I just tried to get in the ball park, you know.
As for Prue going straight back to work, that was actually intentional on my part. I saw Prue as being like my aunt, a workaholic who just can't slow it down. So she'd have wanted to get back to work as soon as possible, I think.
The twins are half-demon, half-witch. That should be obvious. Prue's power is Advanced Telekinesis, as was said in a chapter in S4, which means that she can move things so fast that they explode. Basically her power from Morality Bites, but more focused. It's not the same as Piper's Molecular Combustion, but it is very similar. Saying that she exploded something is a lot simpler than saying "Prue moved X with telekinesis so fast that he exploded" every single time. She would still keep her normal telekinesis as well though, same as Piper kept her telekinesis. As for the twins' powers...
In S4, the twins have the same powers as the Source and the powers that they exhibited in 4x21. However, in 4x21, they were being augmented by the Source's essence. Once it was removed from them, their powers became inactive. They didn't lose them, but they did become inactive, as they were no longer being augmented. They'll have to progress back to that point. In S5, they gained healing and a fire shield, which is why their shield is red rather than Wyatt's blue, and they can combine the power with Wyatt to make a purple force-field, which is what they usually do. They also regained the ability of Flaming. And they also gained the power of Sensing. In S6, so far I have given them the power of Reality Warping, as I have always loved that power. It works like Wyatt's Projection power sort of, but they gained it a lot later than he did Projection, as Wyatt had his Projection power in S5.
As for who's more powerful out of the twins and Wyatt... So that I won't have to answer this question again, power level will go like this for all of the Charmed progeny:
Individually
Phoenix, Wyatt, Tamora, and P.J.
Persephone, Chris, Kat, and Parker.
Pagan, Melinda, and Peyton.
(Paige's son won't have powers.)
Together
Prue's kids
Piper's kids
Phoebe's kids
Paige's kids
(Phoenix and Persephone, along with Tamora and Kat, would be more powerful together as well, due to being twins, with the Phoenix/Persephone pair being more powerful than the Tamora/Kat pair.)
In their specific sibling grouping
(Oldest to youngest like normal, though like I said, Paige's son won't have powers.)
And OMG, thank you! I'm not the only one who hates Grams! I know that most like her, and see her as this model grandmother, but I could never stand her. She's sexist and drove the girls' father away. I honestly can totally believe that she did something to literally keep Victor away from his kids. Hell, she even tried to take the girls' destiny away, as seen in Pre-Witched, and she had no right, especially since by then they were adults. It should have been their choice.