This could be a lethal/non-lethal mutation that requires NO new art ( unless i’m mistaken )
This affects bleeding and the way blood clots, blood can either not clot or it can not clot properly/efficiently
The cub could survive a full healthy life however it wont live to be very old
No birth message.
Month 1: Your Lioness watches carefully over her cub scolding him when he gets too rough, she runs over him/her when he/she gets a scrape and shoos away the others
Month 2: Your lioness still keeps a watchful eye on her cub seeming to almost seclude him from the others
Month 3: While playing with the other cubs he/she trips and cuts their foot on a rock, when you return later you find that they're still slightly bleeding as their mother shoos you away and tends to her cub
ECT.

Males cannot patrol,spar or be kings. And while females can give birth her chances of surviving through the birth is low. To make this worth it she has an increased chance of mutation in her litters.
To try and help a female survive through birth she can be fed alfalfa which would cost GB (Not sure how much it should cost) Cubs will also NEED a broodmother to survive and just simply will die regardless without the careful eye of a lioness.

Pros: Females will have a high chance of mutated cubs ( not sure percent of increase)

Cons: Males cannot be used for anything and females while able to have cubs will need an item to help them survive the birthing. Also any lion will have a short life span due to the fact that blood clotting also gets even rougher at the older ages.|

If possible id love a reason why you support/Dont support. This will help me tweak this.