John Mayer is apparently in the running to become godfather to Pete Wentz and Ashlee Simpson's unborn tot.

The Fall Out Boy star has formed a close friendship with Jennifer Aniston's man – as is clear by anyone who reads their respective blogs.

"Pete and John have been spending a lot of time together lately and they get on so well," says a source.

“They are firm friends. John gets a bad rap and is always portrayed as a bad boy but he's got a heart of gold. Pete and Ashlee know that and they think he would make a great godparent."

There's just one stumbling block to overcome - Ashlee's sister and John's ex, Jessica.

The source adds, "But they are holding back asking him at the moment because they are not sure how Ashlee's sister Jessica would feel about her ex having such a strong link to her new niece."

The emo baby is due in October.