Ireland - Passport & Nationality - Dual Nationality
Unlike in some European countries, taking up Irish citizenship doesn't require renouncing another citizenship. Ireland's Department of Foreign Affairs has no objection to anyone's holding dual citizenship, but it does advise individuals to clarify the position with home governments first.
For more specific information about some countries where you hold citizenship:
Under the nationality laws of some countries, a married person automatically has his or her partner's nationality. Children may also have a parent's nationality even if they were born abroad. If your wife, husband or child is visiting the country of your nationality, you should check with the country's consulate or high commission in the United Kingdom before you travel.