The price of marrying somebody is that you usually marry into their family, too.
Unless your spouse is no-contact with their relatives for whatever reason, part of being a good partner to them is likely going to involve some wrangling of the in-laws. Some people are blessed with the perfect family to join, but that isn’t the case for the majority. Within reason, they simply have to learn to work with what they’ve got.
While it can be important to make an attempt at getting on well with your partner’s family, it is also vital to have boundaries. There are plenty of cases of overstepping parents or difficult siblings causing issues in a relationship that don’t need to be there because nobody is willing to say no to them. At first, it can seem like a green flag when a potential partner is close with their loved ones, but that can quickly turn into a headache as the relationship gets more serious. There is a difference between a healthy family relationship and being totally co-dependent on one another, or even worse, dealing with somebody who walks all over them. They should not be letting family drama get in the way of their marriage.