Fellow medievalists, esp. charter people, a question out of ignorance: how common was it that single people were 'exchanged' as Heloise and Emeline were in the act below (source: The Cartulary of Blanche Countess of Champagne, ed. T. Evergates, p. 58). Thanks!

I thought it looked possibly quite similar to this, which is the De sex aliis cherubim in CCCC 66 p. 100.