When you tame a creature, anyone can tame it after you for skill. However, you cannot retame the same creature for skill if you have more than 50 taming. This is true for every owner owner of the creature. Anyone who has tamed or been an owner of a pet will have a retame difficulty of 0 for that pet. For someone else to come along and retame a creature, there is a difficulty increase, depending on the number of times it has been retamed (which is not the same as how many owners it has had). The chart below illustrates this with an example for a pig.
The number of owners a pet has had will not effect the pet's orneriness in any way (ie. a 4th tamed nightmare will have a taming difficulty of 113.1, but will still have the 95.1 orneriness).
For every person that tames a creature, the minimum difficulty goes up by 6. If 10 people have tamed a creature, the 60.0 (6 x 10) is added to the creature's minimum requirement.