I doubt there is such a minhag. If the bride and groom are both in the same shul or even the same city (which until recently, meant the same thing – multiple shuls in a city is a modern innovation), of course he would be there. Where else would he go? Any such minhag is therefore a recent innovation.
If the wedding is in a distant city, the bride’s family won’t be there on the Shabbos before. That a matter of practicality, not a minhag.