Only the front rows are a chart
The most useful thing to know about ceremony seating is how little of it needs deciding. Guests arrive in a fifteen-minute window, sit for half an hour, and stand up again — there is no dinner to host, no table dynamics to manage, and no board for people to consult on the way in. So assign the reserved rows and leave the rest open. Two rows per side covers immediate family at most weddings; three if you have large families or several grandparents.
Front row is parents, traditionally with the couple's mother closest to the aisle, plus any partner if a parent is remarried. Second row is grandparents. Third, if you use one, is siblings not standing in the wedding party, then aunts, uncles and cousins behind. Reserve those rows visibly — printed signs or a ribbon across the ends — and brief one usher on exactly who belongs there. An unmarked reserved row gets filled by punctual guests who then feel awful being moved, which is a completely avoidable moment.
Sides, and the case for ignoring them
The convention: in a Christian-tradition ceremony the bride's family sits on the left facing the front, the groom's on the right; Jewish ceremonies traditionally reverse it. It is a real convention and older relatives will notice it, so it's worth knowing before you discard it.
The case for discarding it is arithmetic. If one family is bringing sixty people and the other twelve, honouring sides gives you a packed half and a visibly empty half in every photograph down the aisle. A "pick a seat, not a side" sign fixes it in one sentence, fills the room evenly, and has become common enough that nobody reads it as a mistake. Keep the reserved front rows split by family either way — that part isn't about balance, it's about the people who need to be able to see.
Divorced and remarried parents
Give each parent their own row. The parent who raised the couple, or the one they're closest to, takes the front row with their partner; the other takes the second row with theirs, still close enough to see and be seen in photographs. The instinct to seat both at the front together because it looks tidier on paper is the single most reliable source of ceremony tension — and the fix is free, because there is no floor-plan cost to using one more row.
Whatever you decide, tell both parents the arrangement in advance rather than letting them find it out from an usher. Same principle as the reception: the seating decisions that hurt are the ones people discover in public. The reception version of this problem, where the stakes are three hours rather than thirty minutes, is covered in seating chart ideas.
Chart it and print it for the ushers
The layout below is two blocks of four rows with a centre aisle, front rows labelled for reserved family. Rename the rows, drag your family names into the reserved seats, and export a print-ready PDF — one copy for the usher and one for the coordinator is the whole deliverable. Free exports carry a small watermark; the chart and the layouts are free.
The reception is the bigger job and a different document: tables rather than rows, hosted for hours rather than minutes. Build that one from a reception template or the main seating chart maker, and see the step-by-step guide for the order to work in.