Accordingly, his son Nicholas would be the sole heir of Salgó Castle (Börzsöny), which was acquired by Simon alone decades earlier, while Tapolcsány (today Topoľčany, Slovakia) belonged to Frank's branch.
The remaining two castles (Somoskő and Bene) and the surrounding villages became a joint family property, while both branches had to appoint an own castellan, simultaneously.
A year later, his cousin Ladislaus II died suddenly and Nicholas became owner of the whole Szécsényi property, making him one of the richest landowners in the Kingdom of Hungary.
Szécsényi escorted his monarch to Késmárk, Szepesség (today Kežmarok, Slovakia) in March 1423, and was one of the sixteen secular barons and prelates who provided safe-conduct to the envoys of Władysław II Jagiełło, King of Poland.
At the same time, the King founded a collegiate chapter in the town of Buda, at the chapel of Jewish Street, dedicated to God and Saint Sigismund, and donated most of Schallaga's fortune [to the chapter].Mór Wertner was the first historian, who identified "Nikolaus Schallaga" with Nicholas Szécsényi, later also supported by Albert Gárdonyi and Bernát Kumorovitz.
On 22 June 1439, Albert has returned the half of lands Szécsény, Almás and Sztracin (each of them laid in Nógrád County) to Ladislaus III Szécsényi.
However Sigismund maintained the decision of the county assembly and ordered to confiscate half of the Szécsényi wealth in the spring or summer of 1424 (definitely before 19 August, when the King made the first donations from it).
A notorious forger, Gabriel Zomlini confessed during his trial in 1446 that he had falsified a charter in favour of Ladislaus to prevent the confiscation of the Szécsényi fortune.
The document suggested that Simon and Frank received a privilege earlier that was not possible to confiscate the wealth due infidelity, since the other branch had to inherit it.
Sigismund personally visited the confiscated estates in Nógrád and Pest counties, on his way from the wedding of Władysław II Jagiełło and Sophia of Halshany in Kraków to his royal seat in Buda.
His relative Ladislaus Szécsényi tried to pass the castle of Hegyesd as a titular pledge to Nicholas, which he inherited through maternal side, however Simon Rozgonyi, Bishop of Veszprém and his brothers reported his intention to the royal court.
As a result, Sigismund, who has been abroad for years, forbade to Ladislaus to donate the fort to his relative, in his letter written on 25 September 1433 in Mantua, while travelled to the Council of Basel.
In March 1435, the Hungarian Diet which assembled in Pressburg (today Bratislava, Slovakia) began a process against Hedwig, who was accused of poisoning her husband, feared that he could discover her adulterous affair with Szécsényi.
According to a contract from 19 November 1436, he had sent his familiaris John Pelsőci to take over 100 gold ducats from his cousin Ladislaus Garai, Ban of Macsó.
[19] Entrusting his four Venetian friends – doctors John Caldiera, Pietro Tomasini, and trader Alexander Bono and his son Moses Bono – with the execution, Szécsényi, who died unmarried and childless, made his relative Ladislaus Szécsényi as heir of his virtually existed fortune (as considered himself to be their owner), leaving his all castles, towns and villages in Hungary to him, except Szakall, which he donated to the local Benedictine monastery, which had to be re-established.
[21] Historian Pál Engel, who wrote the first study about Szécsényi's life and hardships, considered he was condemned on the basis of false accusations.
[23] After Szécsényi's death, his last will's executors sent Garai various letters and personal messages to request payment of his debt, but all these attempts remained without any response.
As his last will and testament proves, Szécsényi was a literate man, unlike other secular barons in the 15th century, in addition, he also wrote, including love letters (possibly to Hedwig, who spent his life in house custody at Garai's castle).
[22] Further documents were discovered by Martin Štefánik in the Venetian archives, written in mostly Italian dialect, which suggest, in addition to being educated, Szécsényi was "frivolous and pleasure-seeking man, who was more like a Renaissance cavalier and adventurer [...], rather than a medieval Christian knight", according to Dvořáková.
[25] As Szécsényi mentioned his female slaves more extensively than others in his last testament, Dvořáková argues it confirms the justification for the accusations about his uncommitted sexual life, which confronted with the common practice of moral norms in Hungary.