1)
Here it says that that Sha'ul's sons were Yonason, Yishvi and Malkishu'a. Below (31:2) it says Yonason, Avinadav and Malkishu'a, In Divrei ha'Yamim (1:8:33) it says Yonason, Malkishu'a, Avinadav and Eshba'al. And below (Shmuel 2 2:8), it says that Ish Boshes was his son!
1.
Radak: Yishvi is Avinadav. It mentions here and in 31:2 the three who went to war with him. In Divrei ha'Yamim it lists also Eshba'al, i.e. Ish Boshes.
2.
Malbim citing Mahari: Yishvi is Avinadav. It does not mention Ish Boshes, for he was king later, and is known in any case.
