Largest Tarptent I have is a snug fit for two, so doesn't qualify. The Easton Kilo 3P is very roomy for two and will fit a third, and quite a decent weight for a traditional tent (largely because of the carbon poles). A teepee shelter like the Golite Shangri-la 3 is another option--I use one once bug season is over. It too is roomy for two, but for three I think you'd need to suspend it from above and eliminate the pole (or use to poles in an inverted "V."

Cheers,
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--Rick