Can only give you extracts from documents which you may piece together :
Dr. Alexander Adair (d.1740 will 12 Jan 1744?) m. Christian Sterling b.1703. Their dau. Cassandra m. John Moore Kent Co. Ref Charles Co. Pro. lib I.R., No.1, p.256/ sister of Robert Adair (d.1768)of Balto. Co. Chan. Papers, 4123, or 4125.
1770. John Moore to Cassandine Adair. dau. of Robert and Elizabeth Adair. Kent Co. Pro Book DD No 4, f 716-179.
If Cassandra who m. Moore was sister of John Adair then he may have been the brother of Robert Adair, both sons of Alexander Adair ?
Did Capt. John Posey bc1722 in Charles Co., Md, died 1790/91 Chester Co. marry Robert's widow, Elizabeth Adair before June 1769 ?
Robert (Sterling) Adair bc1715-1722 was son of Dr. Alexander Adair of St. Paul's Parish, a surgeon of Calvert Co., who died in 1740/1744. Robert was a Representative for Baltimore Co. and died at his home Oct. 22, 1768.
I wonder if they are related to Robert Sidney Adair ?