If the is on the title deeds he would be entitled to a share of the sale value, however depending on any agreements this may not be 50% if there is a dispute of the amount you could look at going to court and have amounts and agreements look at to have a determination as to how the property should be split.
I shall provide you with a helpful link that will assist you in finding a solicitor/representative near your local area. This will provide you with someone nearby your area who can assist you if required.
I hope this information proved helpful. You will find a local solicitor who deals with these matters on the law society webpage which is as follows;
https://www.lawsoc-ni.org/solicitors (N. Ireland)
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