This gives an opinion bonus (+10 vassal transfer) for each transferred vassal of count+ tier. Each councilor must be eligible for the new position. This situation gives the Duke of Munster a -25 'Wants Control of the County of Desmond' opinion penalty towards you. It decreases with the rank of the target. At any rate, alliances with infidels are extremely unlikely to form. However, eunuchs who are already landed can be granted higher titles such as duchies. This is the main reason why it's a good idea to keep de jure territories together. They are more likely to accept a duchy or a county with many holdings. Use a favor to force your liege to give you a council position of your choice.