Just my husband. The first time he sort of blacked out, he didn't actually fall all the way to the ground, just stumbled a few steps backward and fell into the chair when it hit the back of his knees : ) The second time he knew to keep his eyes away from the action.
Funny story about the first delivery--my in-laws showed up unannounced about 2 hours into my induction. The pitocin was working and my contractions were going in earnest, but I was stalled at 5 cm. I did have an epidural though (yay for drugs!), and my husband had just started the movie that we were going to watch. I believe it was Lilo and Stitch.
Anyway, my in-laws walk through the door and I was pissed. I was wearing one of those ridiculous hospital gowns (wasn't allowed to wear my own nightgown because I was high risk) and I really didn't want them seeing my private areas. My mama raised me right though and I was trying to be a good hostess, even though I was uncomfortable. Then my MIL revealed that they weren't really there for me, they had shown up to take my husband to dinner, lest her poor widdle baby's blood sugar should crash from the hard work of sitting at my bedside, loudly munching the bag of chips that one of the nurses had brought him. So my husband left with them and was gone for 3 HOURS while I was in labor.
I was alone and in labor for 3 HOURS, during which time my water was broken and my membranes stripped, which any woman who has had those procedures done will tell you they can be extremely uncomfortable, especially since my epidural was dialed back because my son's heart rate kept decelerating and the nurse said they needed to encourage me to progress quicker. Apparently MIL told DH that I was hours away from delivering and there wouldn't be much happening anyway, and she somehow figured out how to make this dinner a 7 course meal in the hospital cafeteria. I'm pretty sure they stayed until the cafeteria closed. I was a very unhappy mama.
So although my in-laws were at the hospital for several hours during my labor, I think I maybe saw them for 10 minutes.