It looks like Jennifer Garner (search) will assume a brand-new alias this fall — Mommy.

The "Alias" TV star — spotted in Santa Monica, Calif., Sunday with her beau and "Daredevil" co-star, Ben Affleck (search) — is three months pregnant with their first child, multiple sources close to the duo tell E! Online.

Affleck's spokesman, Ken Sunshine, refused to comment on whether the stork is on the way, insisting, "We don't comment on his personal life." Garner's rep did not return calls.

The happy news comes two weeks after reports first surfaced that the couple had become engaged, a claim Sunshine denied.

E! said Affleck flew Garner's family from West Virginia to California last month for her 33rd-birthday party and later popped the question in private.

Garner was previously wed to "Felicity" star Scott Foley, and Affleck, 32, was once engaged to Jennifer Lopez.