From an online transcript of a history Major/High Sheriff John Welsh of, Anne Arundel Co, Maryland d. 1686 Anne Arundel Co, Maryland
from The Founders of Anne Arundel and Howard Counties, Maryland by Joshua Dorsey Warfield
Major John Welsh, High Sheriff of Anne Arundel County
In 1667, Major Welsh was a Commissioner of Anne Arundel County. In 1675, as the husband of Mrs. Anne Grosse, widow of Hon. Roger Grosse, he was executor of the large Grosse estate. . .
Mrs. Elizabeth (Grosse) Welsh was the mother of Silvester and John Welsh, Jr. The latter was known later as Major and Colonel John. She died before 1675, when Major Welsh married Mary, stepdaughter of Nicholas Wyatt, and half-sister of Sarah (Wyatt) Dorsey, wife of Colonel Edward. .
I do not vouch for the reliability, but that excerpt does mention Major John Welsh -- there's more there on that page at that website w/sources
I don't think a difference in surname constitutes a bar to being related. If it is, then the whole premise of WikiTree will collapse. Relationships are by blood and /or by marriage.