i'm sure he's seen him since we last saw him. unless they decide to tell him about it after the baby is born? which would be just plain stupid if ya ask me. also he's excited cause he acts like it's his 1st kid. we know it isn't. but for one it'll be the 1st kid he has that he can actually raise.
with "Parker" like you peeps have said he has limited time with him so he really isn't raising him. 2ndly if anyone here watches 'Castle"they have a habit where some of the characters have relationships off screen. an example would be his mom dated this old rich dude. we heard about him but i don't think we ever saw him. & if we did it was only once or twice. & he later ended up dying. in short they have relationships on that show that isn't always shown, so 'Bones" i think is a bit like that as well.
we know about "Parker" but we hardly see the kid cause i don't think he is always needed for some episodes. but i do agree that they should have had him on more often this season. after all he's getting a sister. also i think you tend to forget that we do see "Zack" well the actor anyways appear in at least once a season. in season 4 i think it was? or it could have been season 5. he appeared in 'Booths" dream finale.
i dunno it just seems like we see him at least once. as for how this season is so far. it's MILES better than last season by far! even though in the 2nd half it ended up getting a LOT better. & i think it's working having put them together. even though it does feel like they waited far too long.
the way it's written i think is pretty realistic. as well. & on how "Bones" is it really fits on how she is too. in short they are doing a better job writing that than i thought they would. so that's a plus as well. at least i think so.