Jon Hamm is set to become a first-time father at 55 as his wife Anna Osceola is expecting their first child together. In exclusive photos obtained by The Daily Mail, actress Osceola, 38, proudly showed off her growing baby bump in a bikini during a beach day in the Hamptons with the Mad Men star last week. Osceola, who appears to be in her second trimester, glowed in a green two piece which displayed her growing stomach as she took a quick dip. A shirtless Hamm, who wed Osceola in 2023 after previously declaring he lacked the 'marriage chip,' looked giddy as he doted on his pregnant wife during a break in his hectic schedule. The Daily…