No sleeping allowed

I have two daughters who seem to believe that no sleeping is allowed.

Julia, 3 1/2 yrs old, refuses to go to sleep before she yells and screams and cries and thrashes for an hour or so. Almost every night over the past 2 or 3 weeks we have seen some version of this ritual. She will go through various parts of her bedtime routine with no problem but at some point she decides it is necessary to through a tantrum. She's doesn't want to be isolated from the family, we get that but almost EVERY night she seems to forget the end result is the same...she goes to sleep. It might be 2 hours after her bedtime but she ends up asleep. So, no amount of tantruming will change the fact that she will end up asleep.

Jacqueline, 7 mths, refuses to take a nap while laying down. She doesn't sleep though the night yet and she still naps a lot but only when she is being held on her mother's lap or when I have her strapped in the Ergo.

Why won't everybody sleep like normal people?