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Is it Yusof Ishak, first president of Singapore?

Correct, your turn again ;)

Nope. The new chap was long dead before Richard was even born.

Black James Douglas would seriously surprise me, as his coat of arms lacks the heart on the field d'argent:
http://www.twcenter.net/forums/attachment.php?attachmentid=325520&d=1431986266

In fact...

Which Douglas is it, then?

Here's the next one:

Is it William Douglas, 1st Earl of Douglas? (According to the coat of arms it must be a Douglas and the armour looks like 14th century transitional, so it might well fit.)

Aymer is right. It's Konstantin Edouardovitch Tsiolkovsky, one of the founders of modern rocket science.

http://www.twcenter.net/forums/attachment.php?attachmentid=325264&d=1431218512

Well, that one was a hard nut to crack.

It is Ogier Ghislain de Busbecq, a Flemish diplomat in Habsburg services who was ambassador to the Ottoman Empire and his first diplomatic mission was to...

Done.