having a hard time! advice needed!

I recently got married to the love of my life. I'm about to be 20 and he's about to be 24. We are extremely ready to start a family. We been this way since we first met. We have our own house, cars and pay our own bills. We are completely stable. Well my mom keeps making side comments saying "you better wait 3 years to have a baby because I need a break" because my sisters baby just turned 1. She says that she's not ready for another grand baby yet. It breaks my heart because I feel like if me and my husband try to convince and then succeed she will not be happy for us and she will be angry. What do we do. His family can't wait for us to make a tiny human but my moms the only one not on bored. Any advice?