How is Keshav married to Mithila and Minal?

New viewer here 

Can someone please explain how Keshav is married to two women... I mean it's illegal. Plus Saksham I think is Mithila's son while Tejal and Chiraj are Minal's children.... if I am not wrong. 

Thank you 

Saksham, Chirag and Tejal are all siblings and they are the children of Minaal. Mithila was first married to Keshav but Mithila couldn't have children so she allowed her sister Minaal to marry her husband and she loves the children as her own. 

It's never explained how they bypassed the law. 

Oh okay thank you for replying