The 51-year-old "Gravity" star is loving every moment with her family, reported E! online.
"Bryan has officially moved in with Sandra. He still has his home as well, but lives with Sandra full time. They have been spending most of their time together.
"Bryan treats Sandra's children like his own. He really is a great farther figure. Sandra is the happiest she has ever been," a source said.
Bullock is mother to two children Laila and Louis.
"Sandra's favorite thing is to be a mom and take care of Louis and Laila. It's her biggest joy in life," the source said.