A group of six babies born at the same time is commonly referred to as a "set of sextuplets." Sextuplets are part of a multiple birth, which can occur naturally or through assisted reproductive technologies. Each baby in the set is typically numbered (e.g., first, second, third sextuplet) for identification.
If they are human they are Octuplets. If they are dogs they are a Litter.
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If it is a group of calves born from different mothers than you call them a herd of calves or a group of calves. If it is two calves born at the same time from the same mother than they are twins, just the same as human offspring would be called.
quintuplets
1
twins
quadruplet
Impossible
Quintuplets.
Septuplets
Quintuplets
Hendeuplets