I thought it would be good to list things to get a good overview. I mentioned 'Desmonds' in the title as they provide info about Donovan in their experience (I won't go over observations of them as individuals). Every piece of info is accompanied by the chapter number in brackets.
Donovan Desmond: (former) Prime Minister and succeeded + current chairman of the National Unity Party (political party, anti-West) during the war, resigned as Prime Minister afterwards.
"Grave threat to the truce between East and West." - WISE (1)
Visited Damian at Eden upon his request after imperial scholar meeting. Disregarded Loid's attempt of making amends (Anya's punch). Essentially shuts Damian down due his complaints regarding being punched. "Our children may share our blood, but they aren't us. They're essentially strangers. It is impossible to understand strangers. In the end.. people will never truly be sympathetic with each other." (38)
Demetrius has (close to) no contact with him. In the past they had a close relationship, Donovan barely left his side, used to watch him study. - according to Damian who heard stories. (93)
Student at Eden during war, Henderson was teaching. "We will never be free of war ... Human beings are simply liars ... So long as that doubt persisted, history would be doomed to repeat itself ...we can never know the true intentions of others ... and we are hiding our true intentions ... I desire peace as much as anyone ... rather with dialogue instead of weapons ... warring like this is the best we humans are capable of ... I can't imagine an end to war." (99)
Made a rare visit home and asked staff to prepare a family dinner. ~long silent dinner~ "This has been a most worthwhile evening." (106)
Donovan hasn't done anything to Melinda (physical abusement). He has become a completely different man shortly after Damian was born. He began to push away everyone around him and barely spoke to anyone at all, including his wife. (110)
Fell ill and collapsed, he seemed like a different person afterwards - reclusive and foul tempered. (121)
Ordered Melinda not to meet with the assembly member she planned to see without her telling about her work plans of the day. (121)
Acquainted with prof Authen - he was meeting with various scholars. Conversations regarding ways to treat neuroses of soldiers, development new medicines, etc. Mention of former director (Surjay) of Loid's hospital.* (122)
Donovan and Authen haven't met again once since he resigned as Prime Minister. - according to Authen. Can potentially be debunked due last page: "Does Desmond know about this?! Could the plan still be underway?!" (122)
Has been visiting the hospital a lot. During his recent visit he headed to the neurosurgery section, visiting a VIP patient (former Prime Minister Chapman) who's asleep. (138)
Owes Chapman "a great debt". Is here to say his goodbyes - according to *former hospital director Surjay. (138)
"There's something so frustrating about not being able to understand others' thoughts. ... This man (Surjay)... does he still... toward me? Is there really no ulterior motive in... calling... here? Idk... but... maybe it doesn't matter." - Donovan (139-2)
Donovan used to spend time with Demetrius unlike with Damian. He used to console Demetrius when he cried, as well as showing empathy and a genuine smile. (141)
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While this is about Donovan, I'll be mentioning some things about Chapman too since it's in strong relation to him (138-139):
Prime minister and National Unity party's chairman prior to Donovan.
'The one who started the war' gained public reputation.
Strict hospital visitation policy per family's request. Condition not made public.
His doctor is not allowed in, barring medical emergency.
Brink of death, family hasn't visited. - according to Surjay.
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Let me know if I missed anything and I'll edit it!
(Also, I'm pretty much joining the theory that he swapped brains with Chapman. So, the mind in the body of Chapman, who lies in the hospital, is the real Donovan.)