Complex sentence: It is truly unfortunate that nearly all of that noble people's long history in Munster has been lost, having now only the O'Donovans left to maternally represent them in any major capacity.
Split into simpler sentences: It is truly unfortunate that nearly all of that noble people's long history in Munster has been lost. The have only the O'Donovans left to maternally represent them in any major capacity.