Is it Kisses?

We have just added a third buckling after we lost one of our baby boys last week. He is 6 weeks old. He does this thing where he puts his mouth on our mouths and wiggles his lips. He doesn’t try to nibble or anything but he almost breaths our breath and lips our lips and he’ll do it for a pretty long time. Like if we don’t distract him he’ll just keep lipping us. Does anyone have any insight into what he is doing? The woman we bought him from said his grandmother does the same thing. Has anyone heard of this or experienced this? If so is it bad to let him do it? I tried to do some research but couldn’t find anything about this behavior. Thanks in advance for the insight!