He doesn't see them again, Drogo and Primula. They had promised to keep in touch, but Brandybuck Hall is far away, by Hobbit standards, and the letters they write had not been as detailed or frequent as they could have been - and when over the years life moved on and they lapsed in their writing, so had he.
The news comes as a shock to all in the shire; and a nasty business, drowning. (Not as bad as burning, though, nothing is as bad.) He feels a ghosting surge of anger when their deaths had been announced, the injustice and its sheer indiscriminate nature rankling sourly, but his thoughts then turn from the shocked masses to the silent boy, an orphan now, like him.
Frodo, barely twelve and yet too small, looking desperately lost in the crowd of his own relatives.
He strides over decisively, and places his hand on a bony shoulder. The child looks up at him, and there are those eyes again, coloured like the meeting of a sky and sea, and he ignores the pang in his chest at its alien familiarity.
You're imagining things again, Bilbo Baggins.
Instead, he cards a hand through thick black curls (no shocks of grey, no silver beads, no coarse braids, just soft and curled like a perfectly normal Hobbit) and stops everyone short with his best glares and an emphatic speech about "the boy needs a guardian" and "you've done nothing but scare him right off", and "of course I'm taking him home with me, I'm the sanest one among the lot of you."
He marches off with Frodo trailing behind him uncertainly, and neither of them looks back.