2 quick questions

Ive recently started breeding rats I have 3 females and 1 male.
Im curious if it would be ok to hold 2 females from 1 mom and a male from a seperate mom for breeding? The offspring would soley be for snake food no holdbacks.
And secondly I have a female runt Ive grown fond of, runts for breeders tho bad Idea?
Thanks in advance for the help :)

Keep the runt, but don't breed her if you're attached to her. She can have a role in your breeding colony as a companion for resting moms, or help out with the weaned females before you feed them off.

As for the line breeding. I've done line breeding, but only one generation. If I see any defects in the babies (I haven't) I would no longer breed that pair, and find a different un-related male.

Keep very careful records, if you notice any problems breeding the 1/2 siblings, don't breed them again, and add a male from a different bloodline to your breeding stock.

Thanks Robin for the help .
As far as the runt goes Im thinking she has only one eye which Im kindda of partial due to my daughter having one eye. Time will tell if I keep her or not the hubby is against keeping them just to keep tho :(