My Sims Can Not Have Spellcastor Babies

@Dobby11111111111 

If you are getting the weak bloodline trait on the kids, then the game probably is working right.  But you can still send the kids to the Magic Realm when they age up to teens and have them become spellcasters and they will get all the benefits that come with the trait.  There's no difference as far as I can tell.  Since there are no special abilities bestowed on toddlers and children (which I really wish that there were some), it really doesn't matter.

I find that when I have a spellcaster-human couple,  I get more spellcaster babies if the mother is the spellcaster.  Same goes for the other occults for the most part.  

Hope this helps.

It's a chance roll whether they'll be born human or spellcaster, although 5 in a row is quite a remarkable streak!  Since your kids ARE getting the bloodline trait, the only difference really is the chance of being born with crazy eyes and or pointy ears.  Their parent can give them Rite of Ascension when they age up to teen, and skip the mote hunting quest, and they will enjoy the bonuses of the bloodline trait.  In one of my games, L Faba married and had 3 kids, and only one of them was a born spellcaster.