Rondo enters and removes his hat. After a cut he takes it off again.
Although it's not unheard of for a priest not to have met either parent before baptizing their child, it is against canon law to perform a scheduled (rather than emergency) baptism without at least one godparent present. Moreover, the godparents are supposed to take a class before the baptism. Who is T.J.'s godparent?
It is possible that Jane, Frankie, Maura, or some combination of them are T.J.'s godparents.
While TJ is being baptized, Tommy and Lydia are arguing in the background about his last name, Rizzoli or Strawbridge. It was mentioned in the 3rd season finale that TJ was 3 months old. This long after his birth his birth certificate would have been filled out and turned in, so there is no point in arguing over his name for the baptism.