It is very doubtful that the situation that the Sadducees were relating ever took place. It is more probable that they were stating a hypothetical case to complicate the understanding of the resurrection and thereby discredit it.

If you accept their basic supposition (marriage continues in heaven), then their reasoning was correct. It would not be possible to administer marriage in heaven with multiple mates as their story described. Their reasoning wasn’t flawed, but rather the ‘facts’ that their reasoning was based on were not scriptural.

The scriptures speak of two becoming ‘one flesh’ in marriage, and angels are not flesh. Paul said, ‘Flesh and blood cannot inherit the kingdom of God’ (1 Cor. 15:50). Therefore, marriage is an earthly institution limited to flesh and blood mortals and will not exist in heaven. Marriage, as is death, is temporary for mortals while they are on earth. This is why a person whose mate has died, is free to remarry. Marriage pertains only to this life.