Your uncle's son will simply be your first cousin (no times removed), more normally just called a cousin. There is a naming system (nomenclature) for blood relations, which is where terms such as first cousin once removed, or second cousin three times removed, come from. Whilst terms like these may seem complex, they are in fact based on some simple rules. The first, second third etc, order of cousin represents how many generations separate you from the common ancestor of you and the n-th cousin. For example, the first ancestor that you and your uncle's son share is your grandfather, and this is what makes you first cousins. If you and some other person share a great grandfather (but no grandparents, so the first closest relation between you two is a great grandparent) then you are second cousins. If you and some other person share a great, great, grandfather (but no great grandparents, so the first closest relation between you two is a great great-grandparent) then you are second third cousins. This naming system continues indefinitely, up to 100th cousins, 100000th cousins, there is no limit. However, when making a family tree, 5th or 6th cousins is generally the largest difference you get.
The "once removed" or "twice removed" bit would refer to the number of generations difference between the two of you. In the case of you and your uncle's son, you are both of the same generation, so are no times removed. If your cousin were to have a son, that person would be your first cousin (because you share your grandparent) once removed (because there is a generation gap of one generation. More information can be found at en.wikipedia.org/wiki/Cousin which is where I got my information.
The "once removed" or "twice removed" bit would refer to the number of generations difference between the two of you. In the case of you and your uncle's son, you are both of the same generation, so are no times removed. If your cousin were to have a son, that person would be your first cousin (because you share your grandparent) once removed (because there is a generation gap of one generation. More information can be found at en.wikipedia.org/wiki/Cousin which is where I got my information.
