What Could Bruising On Ears On Multiple Individuals Indicate?

This is a strange question, but my son and I just moved into a new apartment about a month ago and two days ago my son woke up with this strange hickey like bruise on his ear lobe...I made note of it and asked him about it and he didn't know how he got it, well this morning I woke with the same bruise in the same spot, is it possible there is some kind of rodent of insect in our house, even though I've found no evidence of any infestation when we moved in. That could cause this?