Well both have Birla genes and wasn't it their granddad Harsh who had the illegitimate son Neil? So it's possible this ema nonsense runs in the family, because it is sort of weird how they both don't seem to have any sense of boundaries or guilt for their actions.
Besides, one can't always pinpoint nature or nurture, it can be both. Moreover, Arohi was certainly no angel, although not as bad as Ruhi. Tbf Abhinav & Ak's parvarish cannot totally erase Abhir's inherent bad impulses/tendencies. Similarly, poppy Abheemanyu cannot be the sole reason Ruhi turned out the way she is (although he did chase a married Akshu), but one can't deny that the Birla fam had several morally questionable members.
Yes, infact both their paternal grand father Harsh Birla and maternal grand father Karthik Goenka had multiple women in lives, Harsh's illegitimate son Neil and Karthik had 3-4 marriages, Naira, the other girl i forgot, then Siraat and obviously he had multiple white days like accusing Naira of his druggie brother's death and then accusing her of cheating, etc, so both Akshara and Arohi, the Mothers of Abhir, Abheera and Ruhi have the genes of the icon Karthik, so we cannot really say whether it is the X chromosome or Y chromosome that dominated the traits of all the messed up children.
In Birla house, amidst all the tragedies, Harsh Birla made sure his son get educated, and if Abhir and Ruhi would be with Birlas now, they'd have education too, however, Goenka house, they all were free loading on wealth of Manish Goenka, except Arohi nobody legit had a proper degree.
Lastly, at least in Birla house, Abhimanyu was taught to love his half brother whereas in Goenka clan, Arohi always hated Akshara, the seed of hatred, jealousy and being harmful to siblings was always there in Naira and Karthik's bloodline, hence we can see the repercussions.