Sam has 8 marbles left after giving 3 marbles/person x 2 people = 6 marbles to Sally and Steve.
Hence, Sam had 8 marbles + 6 marbles = <<8+6=14>>14 marbles in the beginning.
Sam had twice as many marbles as Steve, therefore Steve has 14 marbles / 2 = <<14/2=7>>7 marbles in the beginning.
So now, Steve has a total of 7 marbles + 3 marbles = <<7+3=10>>10 marbles after Sam gave him 3 marbles.
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