Second Wives

Second wives are common in many places, including the US, and (in my humble opinion) there's nothing wrong with it as long as all concerned are happy with the situation.
I'm guessing it's Islam in this case, a religion that allows it but there are rules for the husband to follow, those including fair and equal treatment of both ladies.
As for local attitudes and laws, hopefully a local member will help you with those.

here's a perspective, my grand father had two wives. as of now, none of my friends, aquaintances or family members that I know of has more than one wife.
Another local may have a different take on this.

repeating mistakes is always not a good idea 

My farher-in-law had 2 wives.  He also had 13 kids between the 2 wives.  None of his 8 son or 5 daughter were involved in polygumus marriages. 

It comes with loads of challenges.
For example supporting 15 people was certainly not an easy job for 1 man. 

Also having 2 women and their children always watching to ensure they getting treated fairly and trying to undermine each other.

Also none of my husband's brothers and sisters have 13 kids because no one wants that level of responsibility.