On the Whakapapa Māori Charitable Trust website we list everyone’s birthdate as a multiple of 25 years (i.e. 1700, 1725, 1750, etc.) except where we know the persons date of birth.
Unless we know otherwise, we will list spouses with the same date of birth. As most spouses are only listed in most sources in relation to each other there is usually no problems, even when the relationship crosses generations.
Cross generation relationships
Cross generation relationships do happen, usually an older male with a younger female (though there is at least one relationship where a younger male marries his step-mother to inherit the chieftainship of is father.)
Where we don’t have information on the younger spouses family, the younger member is listed within the older members generation. Sometimes the younger members whakapapa is known, if this happens the spouse will be listed in the same generation as their children. This isn’t a mistake, just the solution we have come up with to keep the 25 year generation gap.