This is a regular recurring theme in the ''FireEmblem'' series, [[IncestYayShipping at least according to segments of the fandom.]] Several of the girls in the player's party seem to admire their brothers a bit too much.
* ''[[VideoGame/FireEmblemJugdral Fire Emblem: Genealogy of the Holy War]]'':
** [[spoiler: Deirdre]] and Lord Arvis, who marry in between chapters 3 and 4 (though she is only confirmed to be his bride at the end of chapter 5). [[spoiler: Having the two hook up and ''breed'' is actually a part of the BigBad Manfroy's plan to create a vessel for his Demon Lord. And through MindControl used on Deirdre and Arvis not knowing they're half-siblings, it happens.]] It is hinted in a few early conversations viewable by the player (though unknown to the protagonist) that this is an incestuous marriage being plotted. And bits of dialog regarding other characters crop up, presumably to get the player's mind on the topic of incest and help him figure out what the villain's plot is.
** This recurs in the second generation when Julia, daughter of [[spoiler: Arvis and Deirdre]], has a crush on [[spoiler: Seliph, son of Sigurd and... Deirdre, too.]] Because the first half of the story wasn't Greek-Tragedy enough.
** In the second half of the game, it's possible to pair [[WhiteMagicianGirl Lana]] and [[HorseArcher Lester]] with their cousins [[FriendlySniper Faval]] and [[TheTease Patty]]. Their mothers are sisters, so from a social standpoint they're cousins. However, their mothers are actually Adean and Briggid - who actually are ''identical twins'', which means that from a genetic standpoint, their off-spring are half-siblings.
** Prince Eldigan and Princess Raquesis are re-written this way in the Oosawa manga adaptation, with them acknowledging in their last talk that they're in love ([[spoiler: with Raquesis almost asking Eldigan to be her first, but he refuses to taint her, settling for an implied LastKiss]]) and hoping there's a ReincarnationRomance deal out there.
* ''VideoGame/FireEmblemAwakening'' has the [[spoiler:Male Avatar/Aversa pairing below. However, they're NotBloodSiblings, as the latter was adopted.]]
* ''VideoGame/FireEmblemFates'' allows the protagonist can marry his or her siblings in ''both'' [[SeparatedAtBirth Hoshido]] and [[NotBloodRelated Nohr]].
** There is a storyline justification, alongside '''''MAJOR SPOILERS:''''' [[spoiler: While the Avatar was forcibly "adopted" by the Nohrians, a late game reveal notes that '''he/she isn't related to his/her Hoshidan siblings at all.''' The Avatar is the son/daughter of Queen Mikoto and a dragon spirit, while the Hoshidan royals are the children of King Sumeragi and his first wife who died before the story began. Sumeragi then married Mikoto and was the Avatar's first ParentalSubstitute before his murder, which makes them step-siblings at most.]] On the other hand, [[spoiler: he/she can also marry their Nohrian brood (''themselves'' all half-siblings; three of them by mistresses and Xander by Garon's actual wife Queen Ecaterina), despite being raised with them since a young age.]]
** Azura can marry Xander and Leo, her step-brothers.
** The book ''The Making of Fire Emblem'' reveals that Leo had a crush on his older half-sister Camilla. Aside from their supports hinting that these feelings still linger a bit, this is downplayed as it's never discussed in his other supports or dialogue.