SB 7.5.36

viṣṇor vā sādhv asau kiṁ nu
 kariṣyaty asamañjasaḥ
sauhṛdaṁ dustyajaṁ pitror
 ahād yaḥ pañca-hāyanaḥ
viṣṇoḥ — unto Viṣṇu; — either; sādhu — good; asau — this; kim — whether; nu — indeed; kariṣyati — will do; asamañjasaḥ — not trustworthy; sauhṛdam — affectionate relationship; dustyajam — difficult to relinquish; pitroḥ — of his father and mother; ahāt — gave up; yaḥ — he who; pañca-hāyanaḥ — only five years old.
Although Prahlāda is only five years old, even at this young age he has given up his affectionate relationship with his father and mother. Therefore, he is certainly untrustworthy. Indeed, it is not at all believable that he will behave well toward Viṣṇu.