The most I have ever heard of prior to this was five in one group, a sow with four cubs several years ago. One of my neighbors saw them and told me about them. My wife had an encounter with four last fall, again a sow with cubs, she has to tell that story herself in order to get the best version of it.
My Grandfather, killed four bears in less time than it will take me to write about it. He didn' t have time to reload and took them all with five shots from that old Winchester pump gun he carried all of the time. This again was a situation with a sow and nearly grown cubs. Before anybody gets their knickers in a twist, at that time in Wisconsin, the 1930' s, Bears were treated as vermin. No season, no limit and probably no license required.
Another neighbor and a friend took two from the same cornfield last fall on consecutive days, both over 300 pounds ( I know the weights because I field dressed and skinned both of them, the smaller of the two was weighed on a certified scale and field dress just at 300#) and there were still more in the area, but nobody ever got a count on what was actually in there.