What to do when you don't have qadha fast and the in laws knows about it and they make you break your fast as soon as you keep in the blessed month of Mahe Rajab. How to get the benefits of fasting in this month when you long for it. Please advise. It's a joint family so fasting cannot be kept hidden.

You do not have to accept their invitation, although it is recommended, and if you did, you are double rewarded.