Hello & welcome to the Resto board.
Older people can often be difficult to date as they tended to wear what they felt comfortable in rather than what was fashionable,however the dress style of both is early-mid 1860's.The pose,sitting side by side is a style we often see on Ambrotypes (on glass) of the 1850's but as this doesn't appear to be one of those (unless you know otherwise) I would suggest early-mid 1860's.If you can tell us more it would help.
jim