For me, I just started Sims 4, and mine consist of 4 comparing on WHAT kind of family I use.
I have 4 for my Vampire Dragon Age AU which consist of: Sera being the oldest sister, Cole being the young brother, my Inquisitor Kiki being the mother, and Rhys being the father. All of them are vampires, and basically they don't age , now the tricky part about this, I do allow Rhys and Kiki to have a baby, but THANKFULLY they only had one baby, a little vampire girl/boy. But sometimes I don't even press "try for a baby" because uh, they got two immortal babies right there Sera, and Cole. It is sweet though that I allow Sera to have a sweetheart, but Cole. Er, he doesn't want anyone.
Fun right? Well either way, 4 is the biggest for me, and then, it becomes too much of a hastle.