Many studies on this but here is one mention:
From PhillyVoice
March 25, 2019
Child Abuse Is 40 Times More Likely When Single Parents Find New Partners
By Amy Wright Glenn
((As of 2016)) “Nearly 25 percent of children in America live with a single parent, usually their mother, though the number of children living with single fathers rose from 1 to 4 percent since 1960.”
“...the documented risk involved in bringing an unrelated adult male into the home. Sometimes referred to as the “abusive boyfriend syndrome,” scholars note there is “a statistically greater potential for instability” in homes where adults and children, who have no biological connection, reside.”
It’s natural, lions will kill the already born cubs when mating with a female, to make sure the next liter is his.