Wyatt Russell’s son is “excited” to be a big brother. The ‘Night Swim’ actor and his wife Meredith Hagner will welcome their second son into the world next month and have been doing their best to prepare little Buddy, who turns three in March, for the upcoming change to their household so believe the youngster will be accepting of the baby. Wyatt told ‘Entertainment Tonight’: “You know, he’s three, so he’s as ready as he can be. “I think he understands what’s gonna happen. He’s a pretty smart little guy. “I think we’re definitely doing our best to prepare him for the fact that, like, there wil…