Relatives of different religions can still take part in Japanese childhood rites such as omiyamairi or Shichi-Go-San.
In Japan, families do not necessarily begin by separating people according to religion. If someone does not have a strong religious reason to avoid shrine rituals, it is often perfectly natural for them to follow the people around them and take part in the usual form of worship.
Japanese people who visit a shrine for omiyamairi or Shichi-Go-San are not necessarily doing so because they have a strong personal belief in Shinto. They may go because it is a family milestone, and then follow the usual shrine etiquette while they are there. For some people, this feels less like declaring a religious belief and more like simply following the custom of the occasion.
So if there is no particular religious reason not to do so, joining the others in the shrine ritual can feel entirely natural.
The situation is different, however, if a relative genuinely follows another religion and believes that participating in worship directed toward another religion would conflict with their faith.
In that case, they can still come to the shrine, watch over the child, join the family photos, and take part in the meal afterward, while choosing not to perform the specific act of worship they cannot accept. Whether they are comfortable attending a formal prayer or blessing ceremony may also depend on their own beliefs, so it is best to discuss that beforehand.
The important point is that the whole family does not need to share the same religious beliefs. If everyone shares the intention of celebrating the child’s growth, many families would not see a reason to force a relative to perform a ritual that genuinely conflicts with their faith.
The family members themselves may not be taking part in omiyamairi or Shichi-Go-San for strongly religious reasons either. Because of that, having one relative from a different religion does not necessarily mean that person has to be excluded from the event.
Usually, people can simply join in with the customs of the occasion. If there is a genuine religious boundary, that particular part can be left out without excluding the person from the celebration as a whole.
What a family needs to share at omiyamairi or Shichi-Go-San is not necessarily the same faith. It is the wish to celebrate the same child.
