The couple split up after Stewart cheated on Pattinson with director Rupert Sanders but he has decided to give their relationship a second chance and they are now living under the same roof, reports contactmusic.com.
"They are living together and have reconciled," said a source.
It is also said that Stewart has agreed to tie the knot with Pattinson as it was recently revealed that he would only get back with her if she is ready for marriage.
"Rob told Kristen the only way he can forgive her affair is if she truly commits to him. Rob has been keen to marry Kristen for quite a while and he doesn't want to get back with her unless he knows she means it for life too," said a source.
"Although Kristen broke Rob's heart he has realised he can't live without her. He never stopped loving her and he believes she still loves him. He is desperate to make it work and wants to give her another chance but not unless she proves she really wants it too," the source added.