Brothers separated and raised in different countries. Read in mid-1990s.

[Christine Angela Chenoweth]

Brothers separated and raised in different countries one in the states by an aunt and one in Russia. They have different fathers but the same mother. One of the fathers was a Jewish scientist killed by the Russians. The other father was in the Russian military. The oldest child who stayed in Russia ended up being a KGB agent. Somehow their paths cross and they find out their true identities.

[Paige]

Brothers
https://www.publishersweekly.com/978-...

[Kris]

Christine, around what year did you read this book? A range of years is fine.

What's the genre (which we need to add to the header/topic title) - e.g., for adults or teens? spy thriller? historical? We also need more plot details in the header.

[Kris]

Here's a detailed plot summary of Paige's suggestion - Brothers by Michael Bar-Zohar - from KirkusReviews.com (in a spoiler tag, due to length):

(view spoiler)[Amazing but true: the major upheavals in Soviet-American policy from the Cuban missile crisis to the abortive coup against Gorbachev were all sparked by a monstrous sibling rivalry between two half- brothers, raised half a world apart. The boys are both sons of Soviet-Jewish poet Tanya Gordon, doomed by her membership in an anti-fascist group and by Stalin's relentless anti-Semitism. To save the life of her son Alex, she abandons her condemned husband, poet Victor Wolf, and marries KGB Col. Boris Morozov, who has time to father another son, Dimitri, before Tanya and then Morozov himself are liquidated. Responding to Tanya's dying wish, Morozov sends Alex to Brooklyn to grow up with Tanya's sister Nina Kramer. After endless crosscutting between scenes from the boys' adolescence—Alex is tormented by kids who call his aunt a Red; Dimitri kills a bully who threatens to unmask him as a traitor's son; Alex enrolls in the Sovietology program at Brown; Dimitri trains for the KGB—the two are ready for their momentous collision: CIA agent Franco Grimaldi, eager to recruit Alex, allows Dimitri to find out where he is and lure him to Paris for a meeting; when Dimitri's recalled to Russia, Alex promptly takes his place with his lover Tatiana Romanov; Dimitri finds out and vows revenge; Grimaldi leaks the runaway lovers' location to Dimitri and stands back while Dimitri strangles Tatiana. There's lots more intrigue to come—in fact, ``Afghanistan, Poland, and Star Wars were for [Dimitri] nothing but pawns in...the deadly game he played against his brother''—as Alex and Dimitri keep looking for new ways to kill, maim, or annoy each other, leaving their messy footprints all over foreign policy until the final, ill-advised twist. (hide spoiler)]