Complex sentence: Some mothers took a leading role in negotiating marriages, as Lady Glenorchy did for her children in the 1560s and 1570s, or as matchmakers, finding suitable and compatible partners for others.
Split into simpler sentences: Some mothers took a leading role in negotiating marriages, as Lady Glenorchy did for her children in the 1560s and 1570s. They could also act as matchmakers, finding suitable and compatible partners for others.