The host line is the first line of the invitation and the one couples rewrite most. It answers a single question — who is inviting these guests — and the answer is normally whoever is paying for the day.
One set of parents. Name them the way they are addressed in life. Formally that is “Mr and Mrs Edward Whitfield”; a softer version is “Helena and Edward Whitfield”; a mother hosting alone is “Mrs Helena Whitfield” or “Helena Whitfield”. Their child is then introduced as “their daughter Charlotte Anne” with no surname, because the surname is already above.
Both families. Two lines, joined by one “and”, the bride’s parents traditionally first, and the couple introduced as “their children”. If one family is contributing far more than the other and you would rather not rank them, skip the whole question with “Together with their families”.
The couple hosting. Open with your own names, or with “Together with their families” and then your names. It is the host line that survives every complication below: it names no household, ranks nobody, and still sounds generous.
Divorced parents. Each household takes its own line, and they are never joined by “and”, which would read as a marriage. The mother’s line goes first. A remarried parent appears with their spouse on one line. Because more than one household is speaking, the couple are given full names rather than “their daughter” — example five shows the whole shape.
A parent who has died. They cannot host, so they move out of the host line and into a line of parentage: “daughter of Mrs Helena Whitfield and of the late Mr Edward Whitfield”. Example six is the full wording.
Stepparents, grandparents, godparents, anyone else. The same rule applies to all of them: a host line names the people doing the inviting, in the form they are called in life, one household per line. Everyone else who matters can be named in the ceremony, in a thank-you line on the wedding website, or in the toast.
A host line in another tradition. Some traditions word this line to a different pattern rather than a variation on the one above. A Chinese card is issued by the parents and states birth order — eldest son, second daughter — which an English host line has no way to carry, and it is headed by the double happiness character rather than by a name. Chinese wedding invitation wording sets out that form, the two banquet times and the lunar date, with eight wordings in English and Chinese.
One last decision: titles. “Mr and Mrs Edward Whitfield” is the traditional form and it puts one name on the invitation for two people. “Mr and Mrs Edward and Helena Whitfield” keeps both. Ask the hosts which they want rather than choosing for them — it is their line, and it is the only part of the invitation that is about them.