Best way to comfort my boyfriend?

So, earlier today, we were both sitting in his room, hanging out and everything, watching a movie on his TV. Then, because he had to be at work by 4:30, we started getting ready to leave around 4. Before we left though, he showed me this picture album, full of pictures of him and his mom, and some other relatives. He lives with his dad, step-mom and sister (maybe half-sister, I'm not sure). And yes, his mom is alive. He'd told me before that she wanted to meet me, and when he was flipping through the pages he got kinda teary, and did that thing where you pinch the bridge of your nose, and apologized like "Sorry, this happens every time I look through it." Him being like that made me feel, not bad or anything, but sad he was sad, so I kinda just leaned on him, rubbing his shoulders and stuff. When he dropped me off, I told him I'd meet his mom, but he was in a rush to get to work, so he just nodded and everything. I'm just wondering, is there any kind of good way to comfort him or anything when his mom might come up in another time like that, when it's just the two of us? Because I really don't like seeing him teary /: It makes me teary.