Feeling Herbert push against him, he does make a small gasp, as he had no reason to expect it, but soon starts to lean into the pushing. His head tilting more into the kiss and puts a hand on his hip.
Until now, all of Tony's kisses had been with Bruce, and each time Tony had taken the other boy by surprise, so kissing someone who not only expected it but kisses back has got him giddy. After all he's still only 14.