Complex sentence: He appointed his young son Mohammad, who is believed to be 30 years old (in 2015), as Deputy Crown Prince, thus making the next succession from cousin-to-brother, as Mohammad is the cousin of Crown Prince Muhammad.
Split into simpler sentences: He appointed his young son Mohammad, who is believed to be 30 as Deputy Crown Prince. Again it shows that the succession is continuing from cousin-to-brother as Mohammad is the cousin of Crown Prince Muhammad.