user-1: I'm looking for a sutta wherein the Buddha explains how beings we meet in this life (family, friends, animals etc.) have all been our parents, friends, loved ones, pets etc. in previous lives. What sutta is that?
Thank you for your time.

user19772: Good householder,
Who one actually meets is a matter of tendency, a matter of past and present upanissays-paccaya (strong condition/dependence causes). The meeting of other being is a matter of Upanissaya (strong condition/relation/foundation, giving into).

'Puggalokpi, upanissaya paccayena paccayo.' Upanissaya-Paccaya

It's because of relation being ones foundation, that one is wise in nourishing relation toward 'the Sublime', toward admirable people, and to turn away from those firmly caught in the world.
In case of preferring what's given not from world-binding sources but from the Triple Gems, from those heading or having already unrelated: Mata Sutta: Mother.

A being who has not been your mother at one time in the past is not easy to find... A being who has not been your father... your brother... your sister... your son... your daughter at one time in the past is not easy to find.

One should be clear that it's hard to ever gain the path if no relation with the/a Sublime Buddha, with the Jewels.
Maybe also good on this topic are the effects of association:

Q&A What's the effect of association with outcasts?
Umgang mit Weisen pflegen - Association with the Wise
Association with the Devas - associated Rebirth
Association with pets - Associated rebith?

[Note that this isn't given for stacks, exchange, other world-binding trades but for gain bound to relation toward escape from this wheel]

user2282: From SN 15.14:

At Sāvatthī.


“Mendicants, transmigration has no known beginning. … It’s not easy to find a sentient being who in all this long time has not previously been your mother.


Why is that? Transmigration has no known beginning. … This is quite enough for you to become disillusioned, dispassionate, and freed regarding all conditions.”


-1: <p>I'm looking for a sutta wherein the Buddha explains how beings we meet in this life (family, friends, animals etc.) have all been our parents, friends, loved ones, pets etc. in previous lives. What sutta is that?</p>
<p>Thank you for your time.</p>
 19772: <p>Good householder,</p>
<p>Who one actually meets is a matter of tendency, a matter of past and present <em>upanissays-paccaya</em> (strong condition/dependence causes). The meeting of other being is a matter of Upanissaya (strong condition/relation/foundation, giving into).</p>
<blockquote>
<p>'Puggalokpi, upanissaya paccayena paccayo.' <a href="https://forum.sangham.net/index.php?topic=7956.0" rel="nofollow noreferrer">Upanissaya-Paccaya</a></p>
</blockquote>
<p>It's because of relation being ones foundation, that one is wise in nourishing relation toward 'the Sublime', toward admirable people, and to turn away from those firmly caught in the world.</p>
<p>In case of preferring what's given not from world-binding sources but from the Triple Gems, from those heading or having already unrelated: <a href="https://zugangzureinsicht.org/html/tipitaka/sn/sn15/sn15.014.than_en.html" rel="nofollow noreferrer">Mata Sutta: Mother</a>.</p>
<blockquote>
<p>A being who has not been your mother at one time in the past is not easy to find... A being who has not been your father... your brother... your sister... your son... your daughter at one time in the past is not easy to find.</p>
</blockquote>
<p>One should be clear that it's hard to ever gain the path if no relation with the/a Sublime Buddha, with the Jewels.</p>
<p>Maybe also good on this topic are the effects of association:</p>
<ul>
<li><a href="https://forum.sangham.net/index.php?topic=9290.msg18900#msg18900" rel="nofollow noreferrer">Q&amp;A What's the effect of association with outcasts?</a></li>
<li><a href="https://forum.sangham.net/index.php?topic=1000.msg3722#msg3722" rel="nofollow noreferrer">Umgang mit Weisen pflegen - Association with the Wise</a></li>
<li><a href="https://forum.sangham.net/index.php?topic=8500.msg14411#msg14411" rel="nofollow noreferrer">Association with the Devas - associated Rebirth</a></li>
<li><a href="https://forum.sangham.net/index.php?topic=8467.msg14208#msg14208" rel="nofollow noreferrer">Association with pets - Associated rebith?</a></li>
</ul>
<p><em>[Note that this isn't given for stacks, exchange, other world-binding trades but for gain bound to relation toward escape from this wheel]</em></p>
 2282: <p>From <a href="https://suttacentral.net/sn15.14/en/sujato" rel="nofollow noreferrer">SN 15.14</a>:</p>
<blockquote>
<p>At Sāvatthī.</p>
</blockquote>
<blockquote>
<p>“Mendicants, transmigration has no known beginning. … It’s not easy to find a sentient being who in all this long time has not previously been your mother.</p>
</blockquote>
<blockquote>
<p>Why is that? Transmigration has no known beginning. … This is quite enough for you to become disillusioned, dispassionate, and freed regarding all conditions.”</p>
</blockquote>
