The owner of these memorials has cited many source records in his biographies for these two individuals. He lists their parents and six children. However, if you examine the records closely and look at other record groups in the localities, it quickly becomes apparent that he has conflated the records belonging to two different couples named "Max" and "Ida". The parents and half of the children listed in these biographies belong to a couple who liveslived elsewhere in the state.
I suspect the author of these bios was led astray by an Ancestry hint which suggests the 1930 Census record of this Newton Massachusetts Max Bretschneider to fill in a gap for the missing 1930 Census record for the Max who didn't live in Boston. If you look at all the records available online, such as city directories, historical newspapers, and court records, you see that the records fall neatly into two separate groups. TheNot only do the records separate themselves neatly by geography, the children's records make it especially apparent, because they fall into two groups of three siblings. If you have a set of six people but their records fall into two groups of three, and both group A and group B only reference each other's records, then you need to step back and reconsider what's going on. Sure, family feuds happen, but it's much more likely that Group A's records don't mention Group B and vice-versa because they don't belong to the same family.
Because of mix-ups like the one shown on Find A Grave, my general rule when I see almost-matching records with not-quite-enough information to be sure is to assume they are for two different people and to. I try andto prove that they aren't the same person (by building out the timeline for each one). If I'm wrong, and the records do belong to the same person, the information in the records will point back in that direction.
Records can provide evidence of fraud, and as part of the Genealogical Proof Standard, we do need to provide an explanation for contradictory information. But it's hard for me to see what an individual would have to gain by deliberately being counted on a census twice. A census is a very different type of record than something like a military enlistment where someone might lie about their age because they were too young but wanted to sign up anyway. Be careful that you aren't basing your conclusion too much on a coincidence of names and ages in the absence of other identifiers.