Wikipedia says (although these statements are unreferenced),
There are three ways in which self views could be conceived and all three are said to be wrong views.
All these views types of identity view fetter one to samsāra, and it is for this reason that they are wrong views.
No-self or Not-self?
by
Thanissaro Bhikkhu ends with,
In this sense, the anatta teaching is not a doctrine of no-self, but a not-self strategy for shedding suffering by letting go of its cause, leading to the highest, undying happiness. At that point, questions of self, no-self, and not-self fall aside. Once there's the experience of such total freedom, where would there be any concern about what's experiencing it, or whether or not it's a self?
Similarly this Ananda Sutta says,
"'What do you think, friend Ananda — Is consciousness constant or
inconstant?'
"'Inconstant, friend.'
"'And is that which is inconstant easeful or stressful?'
"'Stressful, friend.'
"'And is it fitting to regard what is inconstant, stressful, subject
to change as: "This is mine. This is my self. This is what I am"?'
"'No, friend.'
"'Thus, friend Ananda, any form whatsoever that is past, future, or
present; internal or external; blatant or subtle; common or sublime;
far or near: every form is to be seen as it actually is with right
discernment as: "This is not mine. This is not my self. This is not
what I am."
"'Any feeling whatsoever...
"'Any perception whatsoever...
"'Any fabrications whatsoever...
"'Any consciousness whatsoever that is past, future, or present;
internal or external; blatant or subtle; common or sublime; far or
near: every consciousness is to be seen as it actually is with right
discernment as: "This is not mine. This is not my self. This is not
what I am."
"'Seeing thus, the instructed disciple of the noble ones grows
disenchanted with form, disenchanted with feeling, disenchanted with
perception, disenchanted with fabrications, disenchanted with
consciousness. Through disenchantment, he becomes dispassionate.
Through dispassion, he is fully released. With full release, there is
the knowledge, "Fully released." He discerns that "Birth is ended, the
holy life fulfilled, the task done. There is nothing further for this
world."'
In summary perhaps they're 'not mine' because (or if) you choose to disown or not identify with them.
Also, perhaps such thoughts do happen to other people? The Dalai Lama for example says that he likes to see himself as being the same (composed of 5 aggregates) as every one else.