Halakhah for Bekhorot 60:35
רבן שמעון בן גמליאל אומר
But R'Simeon B'Gamaliel says: His sons and the members of his family are also required to accept [these obligations] in the presence of three haberim, because the case of a haber who accepts [these obligations] is not on a par with the case of the son of a haber<span class="x" onmousemove="('comment',' The father, a haber, will be more strict, as he publicly accepted in the presence of three haberim the obligations involved, whereas the son of a haber only sees his father practise these laws. Another interpretation is as follows: The reason, according to the first Tanna quoted above, why the sons and the members of the family of a haber are not required to accept these obligations is because the family of a haber actually seeing these levitical laws observed at home, are not suspected of disregarding them and therefore there is no necessity for them to accept these obligations in the presence of three haberim.');"><sup>15</sup></span>